The invention relates to an improved device making it possible to optimize the transfer of pulverulent materials of varied particle sizes. It relates moreover more specifically to the feeding of pressurized pulverulent material to a pan of a molten metal, for example intended for the casting of metal parts, and more specifically aluminum parts.
As is known, transferring pulverulent materials constitutes a problem, given the physical nature of the material to be transported. This problem is even exacerbated if the particle sizes of the material are not homogeneous. Specifically, these differences in particle size may give rise to local plugs, obviously affecting the transfer proper.
In numerous technologies employing metals, and in particular aluminum foundries, a powder under pressure, with variable particle sizes typically lying between a few tenths and 5 to 10 millimeters, is incorporated in order to enhance the qualities of the aluminum, both from the porosity standpoint and from the mechanical standpoint.
This powder is generally of acid pH and is intended to be mixed with the molten metal in order to optimize its required qualities according to the parts to be produced.
The incorporation of powder into molten metal has long been carried out empirically and manually, in particular by means of ladle-shaped containers of relatively large dimensions, which did not allow reproducibility of the additions thus performed, and hence led to final parts of inhomogeneous quality. Furthermore, the use of a ladle with baths of molten metals makes human protection very precarious, and leads to numerous accidents, and in particular burns.
Automatic facilities allowing the conveying of said pressurized powder from a receptacle by means of appropriate pipes has thus been proposed, the transport of said powder being performed under pressure of an inert gas, in particular argon.
Even so, having regard to the characteristics of the powder, and in particular, given its very inhomogeneous particle sizes, satisfactory progress of the powder through the pipes is not achieved and, consequently, the required quantity is not obtained with regard to the molten metal, and neither is the prescribed quality obtained with regard to the final part to be produced.
The object of the invention is therefore firstly, to propose a device making it possible to transfer pulverulent materials of variable particle sizes with the aid of a pressurized fluid. Additionally, it is aimed at a device which makes it possible to overcome the various abovementioned drawbacks.
It proposes a device for transferring pulverulent materials, comprising:
an enclosure in which the pulverulent material to be transferred is stirred and pressurized, at the lower end of which enclosure a pipe conveys said material toward its place of destination;
a gas inlet, and in particular a compressed air inlet, emerging in the pipe, and the inflow being able to ensure the progress of the material toward said place.
This is device characterized in that at the level of the gas inlet, said pipe forms a nozzle, pointing in the direction of the flow of the material, said nozzle emerging into a second pipe, of substantially the same diameter as the first, and in that the gas inlet emerges at the lower end of the first pipe, outside the nozzle, said gas being introduced into the second pipe by means of a plurality of through-orifices made substantially in the same plane as the lower end of the nozzle and oriented substantially parallel to the direction of flow of the pulverulent material.
Stated otherwise, the invention consists firstly in giving the pipe a particular profile, especially a nozzle shape, which is known to impart an increase in velocity to a flowing fluid, this increase in velocity being moreover optimized on account of the orientation of the gaseous flux intended to ensure progress of the pulverulent material.
According to one feature of the invention, the device comprises two gas intakes, distributed in a diametral manner with respect to the pipe.
Moreover, the securing of the first and of the second pipes is obtained by means of a ring, at which the gas inlet pipes terminate.
As already stated, the invention is more specifically aimed at the feeding of pressurized powder to a bath of molten metal.
This device for feeding powder under pressure to a bath of molten metal, comprising:
an enclosure in which the powder is stirred and pressurized, which enclosure at the lower end of a pipe conveys the powder toward the bath of molten metal;
an inert gas inlet, emerging in the pipe, and the inflow being able to ensure the progress of the powder toward said bath;
is characterized in that at the level of the inert gas inlet, said pipe forms a nozzle pointing in the direction of the flow of the powder, said nozzle emerging into a second pipe, of substantially the same diameter as the first, and in that the inert gas inlet emerges at the lower end of the first pipe outside the nozzle, said gas being introduced into the second pipe by means of a plurality of through-orifices made substantially in the same plane as the lower end of the nozzle and oriented substantially parallel to the direction of flow of the powder.
According to the invention, the two pipes are secured to one another by means of rings. One of the rings is moreover furnished with two lateral orifices, diametrally distributed with respect to its generatrix, at which orifices the inert gas inlets terminate. Obviously, the device can comprise more than two inert gas inlets, and under this assumption, the ring in question is furnished with as many lateral orifices.
Additionally, said ring comprises a partition, oriented perpendicularly with respect to the direction of flow of the powder, and drilled on the one hand with a central orifice, so as to allow the introduction at this level of the lower end of the nozzle and on the other hand, with through-orifices, peripheral with respect to the central orifice, and oriented parallel to said direction of flow, and intended to allow the passage of the pressurized gas toward the pipe.
According to the invention, this device is more especially intended for aluminum foundries.